Physical Activity and Cardiorespiratory Fitness in Tarahumara and Mestizo Adolescents from Sierra Tarahumara, Mexico.

OBJECTIVES: Our purpose was to explore the levels of cardiorespiratory fitness (CRF) and the relationship between CRF, physical activity, and other physical traits in traditional and nontraditional Tarahumara, and Mestizo adolescents from Sierra Tarahumara, Mexico. METHODS: A sample of 87 adolescents aged 16.9 ± 1.2 years (mean ± SD) performed the Margaria step test to quantify CRF. Physical activity was estimated using the International Physical Activity Questionnaire. Blood pressure (BP) and anthropometric measures were taken to estimate body composition and other physical characteristics. RESULTS: Traditional Tarahumara showed higher levels of CRF than nontraditional Tarahumara and Mestizo adolescents (F = 5.5, p = .006). The time allotted to sedentary activities was higher in the Mestizo and nontraditional Tarahumara (χ2 = 10.17, p = .006). In nontraditional Tarahumara, adiposity was associated with CRF reduction (r2 = -.63, p = .00), while vigorous physical activities were positively associated with CRF (r2 = .43, p = .03) and negatively associated with the z-score of body fat (r2 = -.42 p = .03). Finally, CRF was negatively associated with fat percentage (r2 = -.27, p = .00) and systolic blood pressure (r2 = -.09, p = .04) in the Mestizo. In this group, walking activities (r2 = -.25, p = .003) and total physical activity score (r2 = -.11, p = .03) had a positive association with the CRF, while moderate activities had a negative association with the body mass index (r2 = .09, p = .04), and vigorous activities were negatively associated with body weight (r2 = .11, p = .03). CONCLUSIONS: In the sampled nontraditional Tarahumara and Mestizo adolescents, moderate and vigorous physical activities were important factors in determining levels in CRF, fat percentage, and other health parameters.

Biomarcadores óseos y su relación con la densidad mineral ósea en adultas jóvenes y adolescentes en su primer año posparto / Bone biomarkers and its relation with bone mineral density in adults and adolescents during the first year postpartum

La información sobre biomarcadores óseos en adolescentes y adultas durante el periodo posparto es incierta, por lo que el objetivo de este artículo fue analizar el patrón de biomarcadores óseos en adolescentes y adultas a 15, 90, 180 y 365 días posparto (dpp) y su asociación con la densidad mineral ósea (DMO) y lactancia materna. Se realizó un estudio de cohorte en 32 madres adolescentes ≤17 años y 41 adultas de 18 a 29 años de edad en el primer año posparto. Se realizaron medidas antropométricas, DMO y biomarcadores óseos y así como datos del tipo y la duración de lactancia. Como resultados se encontró asociación entre la concentración basal de N-telopéptidos ≤24 μg/L y mayor aumento de DMO. Las adolescentes tuvieron mayor concentración de N-telopéptidos (p≤0.004) y menor concentración de osteocalcina (5±3 vs13±4, p <0.001) que las adultas. La lactancia no afectó el cambio de DMO (p>0.050), ni de biomarcadores óseos. La osteocalcina se asoció con el cambio en DMO (p<0.040). La prolactina fue mayor entre las que practicaron lactancia materna exclusiva (p<0.001). A menor edad menores concentraciones de osteocalcina (p<0.001) y mayores concentraciones de N-telopéptidos (p<0.001). Se concluyó que a menor concentración de N-telopéptidos y mayor de osteocalcina hubo un mayor aumento de DMO, lo cual implica menor aumento de ésta en el grupo de adolescentes. La lactancia no afectó la DMO.

The objective of this study was to describe the trend of bone biomarkers in adults and adolescents women at 15, 90, 180 and 365 postpartum days (ppd) and its relation with bone mineral density (BMD). It was a prospective cohort of 32 teenager’s ≤17 and 41 women from 18 to 29 years old. We evaluated diet, anthropometry, BMD, bone biomarkers and hormonal profile. In all, the concentration of N-telopeptide was higher at 15 days postpartum decreasing during first year postpartum, but adolescents had the highest concentration. The lowest N-telopeptide concentration was associated with highest increasing of the BMD. Osteocalcin concentration was lower in adolescents than in adults women (5 ± 3 vs 13 ± 4 ng/mL, p<0.001) during first year postpartum. Exclusive breastfeeding did not affect the BMD (p>0.050) or bone biomarkers. Osteocalcin concentration was positively associated with bone BMD (p<0.040), breastfeeding did not affect osteocalcin concentrations. Prolactin was higher among women who breastfed exclusively (p<0.001). Age and breastfeeding inversely correlated with bone biomarkers (p<0.001) N-telopeptide and PTHi respectively. We concluded that a lower N-telopeptide concentration and a higher osteocalcin concentration were associated with a higher increasing of BMD, so then, adolescents showed the lowest recovery of the BMD. Breastfeeding does not affect the BMD.

[Bone biomarkers and its relation with bone mineral density in adults and adolescents during the first year postpartum]. / Biomarcadores óseos y su relación con la densidad mineral ósea en adultas jóvenes y adolescents en su primer año posparto.

The objective of this study was to describe the trend of bone biomarkers in adults and adolescents women at 15, 90, 180 and 365 postpartum days (ppd) and its relation with bone mineral density (BMD). It was a prospective cohort of 32 teenager's ≤17 and 41 women from 18 to 29 years old. We evaluated diet, anthropometry, BMD, bone biomarkers and hormonal profile. In all, the concentration of N-telopeptide was higher at 15 days postpartum decreasing during first year postpartum, but adolescents had the highest concentration. The lowest N-telopeptide concentration was associated with highest increasing of the BMD. Osteocalcin concentration was lower in adolescents than in adults women (5 ± 3 vs 13 ± 4 ng/mL, p<0.001) during first year postpartum. Exclusive breastfeeding did not affect the BMD (p>0.050) or bone biomarkers. Osteocalcin concentration was positively associated with bone BMD (p<0.040), breastfeeding did not affect osteocalcin concentrations. Prolactin was higher among women who breastfed exclusively (p<0.001). Age and breastfeeding inversely correlated with bone biomarkers (p<0.001) N-telopeptide and PTHi respectively. We concluded that a lower N-telopeptide concentration and a higher osteocalcin concentration were associated with a higher increasing of BMD, so then, adolescents showed the lowest recovery of the BMD. Breastfeeding does not affect the BMD.

[Adolescents do not lose bone mineral density postpartum: comparative study with adult women]. / Las adolescentes no pierden densidad mineral ósea en el posparto: estudio comparativo con adultas.

OBJECTIVE: To analyze the pattern of bone mineral density (BMD), serum concentrations of estradiol and calcium levels, dietary calcium, body mass index (BMI), and lactation in adolescents and adult women at 15, 90, and 365 postpartum days (ppd). MATERIAL AND METHODS: A prospective cohort study was conducted of 33 adolescents and 39 adult women. Anthropometric and dietetic evaluations were performed, as well as evaluations of bone mineral density in L2-L4 and femur neck. Estradiol concentrations and calcium serum levels were determined. RESULTS: L2-L4 BMD increased by 16% in adolescents, and 3% in adult women from day 15 to 365 ppd. While age was associated with this change (ß=13.779, EE=3.5, p=0.001), lactation was not (ß=-0.705, EE=0.647, p=0.283). The adult women had a higher L2-L4 BMD at 15, 90, and 635 ppd (1.151 vs 0.978 g/cm², 1.195 vs 1.070 g/cm², 1.195 vs 1.123 g/cm², respectively) (p<0.003). CONCLUSIONS: Adolescents' BMD increased three times more than that of adult women. For all women, BMD was dependent of age and independent of lactation.

Changes in bone mineral density of adolescent mothers during the 12-month postpartum period.

OBJECTIVE: Bone mineral density (BMD) loss has been described in adult women in the 12-month postpartum period. However, little is known about the precise BMD pattern in adolescent mothers. The present study aimed to evaluate BMD in Argentinean adolescent mothers followed up during the 12-month postpartum period. DESIGN: Analytical, prospective clinical trial. BMD and body composition were determined by dual-energy X-ray absorptiometry; bone mineral content (BMC) and BMD were measured in the lumbar spine (L2-L4), femoral neck (FN), femur trochanter (TR), total hip (TH) and total body. Changes in BMD and BMC were analysed using ANOVA for pairwise comparisons. Other comparisons were performed with the paired-sample t test and Wilcoxon test; Pearson's correlation coefficient was used to analyse the relationship among continuous variables. SETTING: La Plata, Argentina. SUBJECTS: Adolescent mothers (n 35; 17 years old or less) were recruited within 15 d after delivery. Studies and follow-up were performed at 15 d and 3, 6 and 12 months postpartum. RESULTS: BMD and BMC losses at 3 and 6 months and recovery at 12 months fitted a quadratic curve (ANOVA) at the three sites studied (FN, TH, TR), in total-body BMD (P = 0.000) and BMC (P = 0.038). At hip sites, BMD loss occurred at 3 months (FN, P = 0.000; TR, P = 0.000; TH, P = 0.000) and 6 months (FN, P = 0.000; TR, P = 0.000; TH, P = 0.000) compared with basal values. Percentage BMD loss immediately after delivery up to 6 months was about 5 %. CONCLUSIONS: Adolescents showed significant BMD and BMC losses at 6 months postpartum, with an almost total recovery at 12 months in all sites studied.

Changes in body composition in lactating adolescent mothers

Se evaluaron los cambios en la composición corporal durante la lactancia en adolescentes con condiciones socioeconómicas y sanitarias desfavorables. Se estudiaron 17 adolescentes menores de 17 años, primíparas, sanas, asistidas en la Maternidad de La Plata, Argentina. Las adolescentes se evaluaron en cuatro oportunidades: a los 15 días y a los 3, 6 y 12 meses post-parto, determinando a) consumo dietético, b) actividad física, c) estado nutricional (peso, talla, índice de masa corporal según edad, y composición corporal por suma de pliegues cutáneos), d) características de la lactancia, y e) parámetros de crecimiento del niño. La media de edad de las adolescentes fue 15.06 ± 0.66 años (promedio de edad de la menarca, 11.59 ± 0.80 años). Todas amamantaron hasta los 12 meses, y la leche materna cubrió más del 80 por ciento de la ingesta, con un promedio de 7.06 ± 2.54 tetadas/día. Aunque la ingesta diaria de nutrimentos se mantuvo constante hasta los 6 meses y se observó una disminución no significativa de la ingesta de proteínas, hidratos de carbono y lípidos en los controles del día 15 y los 12 meses, la disminución de la ingesta energética durante el mismo período fue significativa (p< 0.05). La práctica de actividad física en todos los casos fue evaluada como leve durante el período de seguimiento. El porcentaje de masa grasa basal fue 29.85 ± 2.87 por ciento, disminuyendo significativamente a los 6 meses (27.2 ± 3.9 por ciento; p= 0.02) y al año (26.1 ± 3.9 por ciento; p=0.002) de seguimiento. En cambio, no se registraron cambios significativos en la masa magra. En conclusión, las madres adolescentes durante la lactancia mantienen la masa magra, mientras que el peso, la masa grasa y el IMC disminuyen significativamente a partir de los 3 meses post-parto

Changes in body composition in lactating adolescent mothers.

We assessed changes in body composition in lactating adolescent mothers living under unfavorable socioeconomic and sanitary conditions. A total of 17 healthy primiparous adolescents under 17 years of age attending the Maternity Hospital of the city of La Plata, Argentina, were followed at 4 time points (15 days and 3, 6 and 12 months postpartum) to assess, a) dietary intake, b) practice of physical activity, c) nutritional condition (weight, height, body mass index [BMI] according to age, and body composition by the sum of skinfold measurements), d) characteristics of lactation, and e) growth parameters of the child. The mean age of adolescents was 15.06 +/- 0.66 years (mean menarchal age, 11.59 +/- 0.80 years). All adolescents breastfed up to 12 months postpartum, and maternal milk covered above 80% the baby intake (mean 7.06 +/- 2.54 breast feeds/day). While the daily intake of nutrients by adolescent mothers was constant up to 6 months postpartum, there was a modest decrease in that of proteins, carbohydrates and lipids 15 days and 12 months postpartum. The decrease in energetic intake during the same period was significant (p < 0.05). The practice of physical activity was classified as moderate during the follow-up period. Whereas mean basal percent of fat body mass (FBM) was 29.85 +/- 2.87, and decreased significantly at 6 (27.2% +/- 3.9%; p = 0.02) and 12 (26.1% +/- 3.9%; p = 0.002) months postpartum, changes in lean body mass (LBM) were not significant. In conclusion, lactating adolescents maintained LBM, whereas weight, FBM and BMI decreased markedly from 3 months postpartum.

leucine catabolism in mammary tissue, liver and skeletal muscle of dam rat during lactation and weaning

Background. This study designed to determine the effect of lactation and weaning on the catabolism of branched-chain amino acids (BCAA). Methods. Rates of transamination and oxidation of leucine and branched chain a-ketoacid dehydrogenase(BCKD) activity were mesured in homogenates of mammary gland, skeletal muscle and liver on day 12 of lactation and 24 h after separation of dams from the litter (weaning). Results. Lactating dams consumed 250 percent more protein than control rats, extra protein is required for protein synthesis by the mammary gland, the extent to which the excess of amino acids consumed during lactation is utilized or oxidized by different tissues is not known. The rate of transamination of [1-14C] leucine by mammary tissue of lactating dams was sixfold higher than in virgin rats. The rate of transamination remained elevated fourfold in post-weaning dams. Rates of transamination were three times higher in mammary tissue than in muscle of lactating dams. Rate of oxidation [1-14C] leucine by lactanting mammary tissue was tenfold higher than in control tissue. Conclusions. The capacity of mammary tissue for transamination and oxidation of leucine increased greatly during lactation, suggesting that the mammary gland may play an important role in the catabolism of BCAA during lactation

Significance of lipid consumption during lactation

Los lípidos de la leche humana constituyen la principal fuente de energía para sostener el crecimiento óptimo del lactante. El contenido y la composición de los lípidos de la leche tiene como origen, los ácidos grasos provenientes de tres fuentes: la dieta, la movilización de reservas grasas corporales acumuladas durante el embarazo y la síntesis de novo por la glándula mamaria. Con base en esto, el consumo y la composición de los lípidos de las dietas así como el estado nutricio, específicamente el porcentaje de grasa corporal de la mujer al instalarse la lactancia, son factores que mantienen estrecha relación con el contenido y composición de los lípidos de las dietas así como el estado nutricio, específicamente el porcentaje de grasa corporal de la mujer al instalarse la lactancia, son factores que mantienen estrecha relación con el contenido y composición de los lípidos de las dietas así como el estado nutricio, específicamente el porcenjate de grasa corporal de la mujer al instalarse la lactancia, son factores que mantienen estrecha relación con el contenido y composición de los lípidos de la leche y por tanto con el contenido energético que se brinda al infante. La evidencia para sugerir que las reservas corporales de grasa subsidian importantemente la demanda impuesta por la lactancia, y en condiciones nutricias subóptimas en que las reservas grasas son mínimas, el consumo de lípidos de la dieta es fundamental. Es necesario esclarecer los mecanismos fisiológicos reguladores involucrados en la utilización de los lípidos a partir de la dieta para la síntesis de la leche, información que tendrá gran valor práctico, ya que permitirá desarrollar dietas óptimas para la mujer que amamanta

Alanine aminotransferase activity in mammary tissue, muscle and liver of dam rat during lactation and weaning

Transamination reaction is the first step in the catabolism of most of the L-amino acids. Alanine is an important molecule in the inter-organ nitrogen transport, conveying them from muscle to the liver Amino groups from this amino acid are generally first transferred to alfa-ketoglutarate in the cytosol of liver cells to form glutamate and leaving behing the corresponding alfa-keto acid analog. Measurements of the alanine aminotransferase (EC2.6.1.2.) activity were compared in liver, mammary gland an skeletal muscle in virgin, lactating and weaning dam rats. In this study liver was the principal tissue involved in alanine transamination, while muscle showed a reduction in the enzyme activity during lactation. Results indicate an increase in alanine aminotransferase activity in the mammary gland during lactation and weaning when compared with virgin rats. This suggest that mammary gland during lactation is an importan extra-hepatic tissue involved in the metabolism of alanine and probably shunted into hte pathways for amino group metabolism in terms of nitrogen economy

Maternal nutritional status and milk volume. Is there a cause-effect relationship?

Se revisaron los estudios disponibles sobre la lactancia humana para obtener algunas respuestas acerca de los efectos del consumo materno de alimentos, el tamaño corporal, la adiposidad, y el estado socioeconómico sobre la producción de leche. Las evidencias publicadas hasta la fecha, son insuficientes para permitir respuestas definitiva, pero se puede sacar una coclusión general: el volumen de leche varía poco entre madres con consumos energéticos, tamaños corporales, y situaciones económicas, con un amplio margen de variación. Existe gran necesidad de estudios más controlados que enfoquen la relación entre el balance materno de energía y la producción de leche